In typical wireless system that includes a transmitter and a receiver, the receiver is not only sensitive to the wanted radio frequency (RF) input (RFwanted), but also to the harmonics (e.g., 2*RFwanted, 3*RFwanted, 4*RFwanted, 5*RFwanted, . . . ). Frequency components at these harmonics may block or interfere with the wanted frequency channel.
Band filters are employed to filter out unwanted frequencies outside of the RFwanted frequency band. However, these filters typically attenuate the unwanted frequencies to a level instead of completely or substantially removing the frequency components, especially harmonics, from the RF input.
A harmonic filter is used to eliminate the harmonic distortion caused by appliances. Harmonics are currents and voltages that are continuous multiples of the fundamental frequency of 60 Hz such as 120 Hz (2nd harmonic) and 300 Hz (5th harmonic). Harmonic currents provide power that cannot be used and also takes up electrical system capacity. Large quantities of harmonics can lead to malfunctioning of the system that results in downtime and increase in operating costs. The second harmonic would have a frequency of 120 Hz; the third harmonic would have a frequency of 180 Hz and so on.